Create a function that converts a string of letters to their respective number in the alphabet.
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | ... |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | ... |
alphNum("XYZ") ➞ "23 24 25"
alphNum("ABCDEF") ➞ "0 1 2 3 4 5"
alphNum("JAVASCRIPT") ➞ "9 0 21 0 18 2 17 8 15 19"